• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.32 no.3
• /
• pp.44-52
• /
• 2024

The go-around procedure plays a crucial role in aviation safety, allowing pilots to abort unsafe landings and attempt a new approach. While existing studies have primarily focused on predicting the onset of go-arounds, relatively little attention has been paid to evaluating aircraft stability and performance after a go-around has been initiated. This study aims to address this gap by systematically assessing the dynamic response and stability of aircraft following a go-around using Quick Access Recorder (QAR) data. The methodology involves classifying go-around events into 'near-ground' and 'at-altitude' categories, and analyzing changes in pitch, descent rate, engine performance, and environmental factors after the initiation of the go-around to evaluate its stability and efficiency. The XGBoost machine learning algorithm is employed to model the aircraft's response post go-around and to predict stability across various go-around scenarios. The findings from this study provide insights that can enhance the safety and efficiency of go-around procedures through systematic analysis of QAR data, contributing to improvements in operational protocols and pilot training programs.

• Nuclear Engineering and Technology
• /
• v.56 no.10
• /
• pp.4437-4445
• /
• 2024

During the process of bilateral teleoperation, operators not only need to perform complex maintenance tasks but also have to constantly monitor the safety of the operation, leading to reduced operational efficiency. Therefore, in this paper, we introduce a shared autonomous scheme that intervenes in the operator's command input when necessary, autonomously ensuring the safe operation of the manipulator by employing a rolling horizon planning controller based on Nonlinear Model Predictive Control (NMPC). This controller considers the motion boundaries and collision avoidance constraints of the manipulator, accompanied by the design of corresponding objective functions. To validate the effectiveness of the proposed method, we conduct tests on collision-free trajectory tracking and comprehensive performance with collision constraints, confirming the feasibility and excellent performance of the approach.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.2
• /
• pp.271-278
• /
• 2000

In this study the effect and applicability of viscoelastic dampers on the seismic reinforcement of steel framed structures are investigated in the context of the performance based design approach. The effect of the damper on dissipating the input seismic energy was investigated with a single degree of freedom system. For analysis models a five-story steel frame subjected to gravity load, a ten-story and twenty-story structure subjected to gravity and wind load were designed. The code-specified design spectrums were constructed for each soil type and performance objective, and artificial ground excitation records to be used in the nonlinear time history analysis were generated based on the design spectrums. Inter-story drift was adopted as the primary performance criterion. According to the analysis results, all model structures turned out to satisfy the performance level for most of the soil conditions except for the soft soil(operational level). It was also found that the seismic performance could be greatly enhanced, and the structures were led to behave elastically by installing viscoelastic dampers on appropriate locations.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.9
• /
• pp.1-9
• /
• 2011

In this paper, we propose an efficient method to create clusters of geographically distributed base stations which cooperatively transmit signals in cellular mobile communication systems. The proposed method utilizes a sequential selection approach to choose candidate base stations which can provide maximum weighted sum-rate gain when they participate in the cooperative transmission with the existing cluster. In particular, the proposed method limits the maximum number of base stations in a cluster by considering the system operational and implementation complexities. Moreover, the combinations of clusters dynamically change along with variations of channel environments. Through computer simulations, performance of the proposed method is verified by comparing with the non-cooperative transmission method and the static clustering method. Numerical result shows that the proposed sequential selection based clustering method is especially advantageous for the performance improvement of lower percentile users in terms of average throughput, and thus the proposed method can effectively improve the fairness among users.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.4
• /
• pp.750-759
• /
• 2015

This paper focuses on reverse simulation methods to find and analyze the required performance of a defense system under a given combat effectiveness. Our approach is motivated that forward simulation, that traditionally employs the effectiveness analysis of performance alternatives, is not suitable for resolving the above issue because it causes a high computational cost due to repeating simulations of all possible alternatives. To this end, the paper proposes a reverse simulation software architecture, which consists of several functional sub-modules that facilitate two types of reverse simulations according to possibility of inverse model design. The proposed architecture also enable to apply various search algorithms to find required operational capability efficiently. With this architecture, we performed two case studies about underwater and anti-air warfare scenarios. The case studies show that the proposed reverse simulation incurs a smaller computational cost, while finding the same level of performance alternatives compared with traditional forward simulation. Finally we expect that this study provides a guide those who desire to make decisions about new defense systems development.

• Journal of Korea Port Economic Association
• /
• v.30 no.3
• /
• pp.89-120
• /
• 2014

The purpose of the study is to suggest a new approach to the terminal operators in order for them to efficiently control their operation cost and support the strategic decision making system and build a performance evaluation process through the systematic cost analysis approach. This study implemented terminal cost analysis based on the traditional cost system, ABC and TDABC and compared the results of each approach. Throughout the study, the usefulness of TDABC was proved in finding operational problems and suggesting countermeasures for improving cost effectiveness and minimizing unused cost.

• Smart Structures and Systems
• /
• v.29 no.1
• /
• pp.17-28
• /
• 2022

The cable component of cable-stayed bridges is gradually impacted by weather conditions, vehicle loads, and material corrosion. The stayed cable is a critical load-carrying part that closely affects the operational stability of a cable-stayed bridge. Damaged cables might lead to the bridge collapse due to their tension capacity reduction. Thus, it is necessary to develop structural health monitoring (SHM) techniques that accurately identify damaged cables. In this work, a combinational identification method of three efficient techniques, including statistical analysis, clustering, and neural network models, is proposed to detect the damaged cable in a cable-stayed bridge. The measured dataset from the bridge was initially preprocessed to remove the outlier channels. Then, the theory and application of each technique for damage detection were introduced. In general, the statistical approach extracts the parameters representing the damage within time series, and the clustering approach identifies the outliers from the data signals as damaged members, while the deep learning approach uses the nonlinear data dependencies in SHM for the training model. The performance of these approaches in classifying the damaged cable was assessed, and the combinational identification method was obtained using the voting ensemble. Finally, the combination method was compared with an existing outlier detection algorithm, support vector machines (SVM). The results demonstrate that the proposed method is robust and provides higher accuracy for the damaged cable detection in the cable-stayed bridge.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.10
• /
• pp.4418-4425
• /
• 2012

The demand on applying the performance-based logistics (PBL) in the operational phase of the weapon systems development is increasing these days. Therefore, the enhancement of the PBL concept and process needs to be done. This is the objective of the paper. As a method of approach, a modeling method is adopted to cover the whole life cycle of the weapon systems development from the concept development to the operation. The modeling results for the PBL process yield an useful suggestion for improvement. Also, by analyzing the interrelationship model between the PBL process and the integrated logistics support (ILS) procedure, it is possible to take advantage of the PBL concept in the ILS elements development, which is usually carried out from the beginning of the development phase, a lot earlier than the operational phase. Note that the PBL concept has been restrictively applied in only the supply support among many ILS elements up until now. However, the results obtained in the paper can make it also possible to consider the availability, reliability, logistics support, cost and so on from the early phase of the weapon systems development.

• IEIE Transactions on Smart Processing and Computing
• /
• v.6 no.3
• /
• pp.158-167
• /
• 2017

Internet-based social and interactive video applications have become major constituents of the envisaged applications for next-generation multimedia networks. However, inherently dynamic network conditions, together with varying user expectations, pose many challenges for resource allocation mechanisms for such applications. Yet, in addition to addressing these challenges, service providers must also consider how to mitigate their operational costs (e.g., energy costs, equipment costs) while satisfying the end-user quality of service (QoS) expectations. This paper proposes a heuristic solution to the problem, where the energy incurred by the applications, and the monetary costs associated with the service infrastructure, are minimized while simultaneously maximizing the average end-user QoS. We evaluate the performance of the proposed solution in terms of serving probability, i.e., the likelihood of being able to allocate resources to groups of users, the computation time of the resource allocation process, and the adaptability and sensitivity to dynamic network conditions. The proposed method demonstrates improvements in serving probability of up to 27%, in comparison with greedy resource allocation schemes, and a several-orders-of-magnitude reduction in computation time, compared to the linear programming approach, which significantly reduces the service-interrupted user percentage when operating under variable network conditions.

• Journal of Korea Society of Industrial Information Systems
• /
• v.16 no.1
• /
• pp.1-8
• /
• 2011

Efficient power management plays a crucial role to strengthen competitiveness in the market of portable mobile commodities. This paper presents a proactive power management technique, called by Energy-Aware Scheduling policY (EASY), to exploit the sleep time information of running applications. Different from previous power management approaches focusing on power conservation in standby mode, the proposed scheme characterizes each application program's operational characteristic in active mode by observing how long the task stays in sleep state of CPU scheduler. Based on the measured sleep time, the proposed EASY speculates an adequate CPU clock frequency according to the current CPU workload and scales the frequency directly to the predicted one. Experimental results show that the proposed scheme reduces the power consumption by 10-30% on average compared to traditional DPM approach, with a minimal impact on the performance overhead.